The speed of sound in air at 20°C is approximately MCQ with Answer and Explanation

Explanation:
Leading zeros not significant. '450' has three digits, but the trailing zero after decimal is significant (4,5,0). So 3 significant figures. 0.00450 is 3 SF.

Explanation:
Potentiometer uses null method: at balance, no current flows through cell, so measured voltage equals true EMF (no internal resistance drop). Memory aid: 'Null method ⇒ zero current ⇒ accurate EMF measurement'. Experimental physics concept frequently tested in competitive exams to verify understanding of precision measurement techniques.

Explanation:
Torque τ = r × F, so dimensions [L][MLT⁻²] = [ML²T⁻²]. Work W = F·d, dimensions [MLT⁻²][L] = [ML²T⁻²], identical. Momentum is [MLT⁻¹], force [MLT⁻²], power [ML²T⁻³]. Though torque and work have same dimensions, they are physically distinct: torque is vector (rotational effect), work is scalar (energy transfer). Memory tip: 'Torque and work share [ML²T⁻²]; but torque = rF sinθ, work = Fd cosθ'. This dimensional analysis question tests ability to compare quantities, frequently appearing in competitive exams. Always verify dimensions but remember physical context differs.